This is going to sound unintentionally cryptic, but... it's the fact that it's a photo.
What I mean is that it's a very nice pose (the right balance of tension & relaxation), body angle, lighting & general setting, which work to enhance rather detract from the undoubted good fit & general coordination of the clothes. You can see this effect play out in a less dramatic way in all the member photos posted here (and in fact, that's maomao in the pic). Lighting, pose, setting and comfort in front of the camera make massive differences to the impact an outfit has. Now, you can still usually tell which outfits would still be to your preferred taste IRL or not, but you do have to take the photography into heavy account too.